INCREASE AT PEDESTRIAN HEIGHT IN … HEAT CONTRIBUTION TO AIR TEMPERATURE INCREASE AT PEDESTRIAN...

ANTHROPOGENIC HEAT CONTRIBUTION TO AIR TEMPERATUREINCREASE AT PEDESTRIAN HEIGHT IN SINGAPORE’SHIGH DENSITY CENTRAL BUSINESS DISTRICT (CBD)

Daniel HII Jun ChungProf. WONG Nyuk HienDr. Steve Kardinal JUSUF

20 July 2015

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CONTENT

• INTRO (UHI & ANTHROPOGENIC HEAT)• SITE MEASUREMENT• PRELIMINARY STUDIES (ROADSIDE MEASUREMENT)• PRELIMINARY STUDIES (CFD SIMULATION)• CONCLUSION & FUTURE WORK

UHI

Representation of the possible causes of the UHI effect. (Toparlar et al.,2014)2

ANTHROPOGENIC HEAT

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Conceptual representation of the urban energy balance for a balancing volume that reaches from the depth where no exchange with the subsurface is found (zb) to the measurement

height on a tower above the urban ecosystem (zt). (Grimmond and Christen, 2012)

Q* + QF = QH + QE + ΔQS

Flowchart of the LUCY global anthropogenic heat. (Allen et al., 2011)

QF = QM + QV + QB

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Ohashi et al. (2003) 1-2°C temperature rise within the building canopy. Narumi et al. (2003) Osaka resulted 1°C temperature rise compared with baseline simulations.

Bohnenstengel et al. (2013), Chen et al. (2009); Kikegawa et al. (2014); Krpo et al. (2010); Li et al. (2014); Fan & Sailor (2005); Jusuf & Wong (2009) Anthropogenic heat contributes 0.4 oC - 3oC to the air temperature.

ANTHROPOGENIC HEAT & AIR TEMPERATURE RISE

ANTHROPOGENIC HEAT IN SINGAPORE

5Singapore’s diurnal and weekly variation of anthropogenic heat emissions. (Quah & Roth, 2012)

𝑄𝑉 @ COM,HDB, RES

𝑄𝐵 @ COM,HDB, RES

𝑄𝐹 Weekday VS. Weekend @ COM

𝑄𝐹 % between COM,HDB, RES

ANTHROPOGENIC HEAT

Annual energy consumption per capita versus combined total of annual heating and cooling degree days (°C) for countries with a population greater than 1 million for 2005. (Lindberg et al., 2013)

Singapore

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City: Tokyo London Guangzhou Singapore Hong KongMotor Vehicles (per 1,000 people): 350 (cars) 317.2 (cars) 150 149 77Population Density (/sqkm): 6,029 5,285 1,708 7,669 6,516H/W Ratio: 0.4142 0.47 0.8 2.45 2.99 / 4.01

Vertical obstruction angle restrictions in different cities. (Ng, 2009 & Ng, 2012)

Cities population and vehicles density

*H/W = Height to Width

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ANTHROPOGENIC HEAT

Number of cars per 100 persons and road density (km/sqkm). (LTA, 2014)

Year Amount

2002 245,000

2003 244,000

2011 300,000

2012 292,000

Average daily traffic volume entering the CBD. (LTA, 2014)

Year Amount2002 706,9562003 711,0432011 956,7042012 969,910

Motor vehicle population. (LTA, 2014)

Public bus fleet/million persons.(LTA, 2014)

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ANTHROPOGENIC HEAT

SITE MEASUREMENT

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The URA Masterplan showing the plot ratio figures of the measurement site at the CBD above and the new Marina Bay development below. (URA, 2014)

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Lamp post locations on site.

SITE MEASUREMENT

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A weather station located at the high H/W Ratio part of Robinson Road on a clear, sunny day with profiles of solar radiation, air temperature and wind speed.

Onset HOBO U30-NRC weather station kit.

SITE MEASUREMENT

Park(Baseline)

Water UndergroundCarpark

High H/W Ratio

BBQSatay

Weather Stations on CBD Site

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SITE MEASUREMENT

-Shading, cooling effect, idling vehicles, openness.

TrafficLight

Junction

Taxi Bus CanyonEdge

OverheadBridge

Weather Stations on CBD Site

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SITE MEASUREMENT

-Shading, cooling effect, idling vehicles, openness.

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Weekdays

Weekends

Weekdays and weekends (February 2014) air temperature at 3.5m above ground (MR_ES=Maxwell Road_Edge of Site, RR_BS=Robinson Road_Bus Stop, BTS_BBQ=Boon Tat

Street_Barbeque Stalls, TAP_TC=Telok Ayer Park_Trees Canopy, RR_HWR=Robinson Road_High Height-to-Width Ratio, CS_TJ=Cecil Street_Traffic Junction,, CS_TS=Cecil Street_Taxi Stand, MC_OB=McCallum Street_Overhead Bridge, RR_WF=Robinson Road_Water Feature, SW_CPE=Shenton Way_Car Park Entrance).

PRELIMINARY STUDIES (Weather Stations)

PRELIMINARY STUDIES (Weather Stations)

15Air Temperature distribution between weekdays and weekends (Feb 8-28, 2014) of the 5 locations.

The weekends for the month are 8th, 9th, 15th, 16th, 22nd and 23rd February 2014.

• Maxwell Road-Edge of the Site (MR_ES)

• Telok Ayer Park-Tree Canopy (TAR_TC)

• Robinson Road-Bus Stop (RR_BS)

• Robinson Road-High Height/Width-Ratio (RR_HWR)

• Boon Tat Street-BBQ (BTS_BBQ)

Type

WeekdayWeekend

PRELIMINARY STUDIES (Roadside Measurements)

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Fluke TiR125 thermal imager.

Roadside measurement at the bus stop in the urban canyon in the afternoon.

Bus surfaces under thermal imaging.Roadside measurement equipment

on the 1.2m high tripod.

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282930313233

0 500 1000 1500 2000 2500 3000 3500 4000Tem

pe

ratu

re (

°C)

Time (sec.)

Temp & Bus Count (5 second interval (5:50-6:50PM, 16Feb2014 Weekend)

Temp (degC) Bus CountTemperature and bus count during rush hour of a weekend

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29303132333435

0 500 1000 1500 2000 2500 3000 3500 4000

Tem

pe

ratu

re (

°C)

Time (sec.)

Temp & Bus Count (5 second interval (5:50-6:50PM, 17Feb2014 Weekday)

Temp (degC) Bus Count

WEEKEND

WEEKDAY

Temperature and bus count during rush hour of a weekday 17

PRELIMINARY STUDIES (Roadside Measurements)

SLAB PLAN ELEVATION POINT PLAN

Computational Fluid Dynamics (CFD) SimulationFluent 15: Realizable K-Epsilon with buoyancy, solar load model & S2S radiation, transient

H/W 2 & 4(8 & 16 stories)

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PRELIMINARY STUDIES (CFD Simulation)

North & East Wind Directions 2m Pedestrian Height2.3m/s @ 15m.

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Parallel Flow (Plan) Perpendicular Flow (Plan)

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Parallel Flow (Left Elevation) Perpendicular Flow (Left Elevation)

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22Without and with bus heat.

Bus Heat

YesNo

Density Comparison – Slab 8 stories VS. Slab16 stories perpendicular flows

Higher density (floors) is worse in terms of heat trap & low wind speed, heat trapped by recirculating zonesLower density (floors) enables the heat to dissipate over the shallow canyon

Slab 8 stories Slab 16 stories 23


Density Comparison for Perpendicular Flow (Section View)

Slab 8 stories VS. Slab 16 stories 24


Density Comparison – Slab 8 stories VS. Slab 16 stories parallel flows

Higher density (floors) has better channeling effect (concentrated), higher wind speed, lower heat concentrationLower density (floors) can also release heat but not as fast

Slab 8 stories Slab 16 stories 25


Density Comparison for Parallel Flow (Plan View)



Density Comparison for Parallel Flow (Section View)



Form Comparison – Slab 16 stories VS. Points16 perpendicular flowsPoints are better at dissipating heat and higher wind speed because of porosity

Points 16 stories VS. Slab 16 stories28


Form Comparison for Perpendicular Flow (Plan View)

Points 16 stories VS. Slab 16 stories 29


Form Comparison for Perpendicular Flow (Section View)

Points 16 stories VS. Slab 16 stories 30


Wind flow regulates the air temperature inside the canyon well by parallel flow. Higher H/W ratio receives better channeling effect causing higher wind speed and more shading.

Higher H/W ratio cases has higher air temperature and lower wind speed with for perpendicular flow.

If design against predominant wind direction, form permeability is more important while for design with predominant wind direction, density may help to create better urban ventilation.

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Ratio for simulationCars : Buses : Motorcycles : Goods Vehicles = 67 : 2 : 15 : 16(*2 covers 2/3 of street)

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FUTURE WORK (CFD Simulation)

View of the 100 vehicles in the canyon – towards worst case scenario.33


Air temperature, wind velocity values taken at 10 spots (5 on left pedestrian, 5 on right pedestrian) in the canyon.

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North Wind Flow

Air Temperature

Highest average canyon air temperature, lowest canyon wind velocity

North East Wind Flow

Wind Speed

Medium average canyon air temperature, lowest canyon wind velocity

Lowest average canyon air temperature, lowest canyon wind velocity

East Wind Flow

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Parallel VS. Perpendicular Flow Difference (Plan)

Parallel flow has higher wind speed, lower recirculating zonesPerpendicular flow has lower wind speed, higher temperature because of recirculating zones

Parallel Flow VS. Perpendicular Flow 36


Parallel VS. Perpendicular Flow Difference (Section)

Parallel flow has higher wind speed, lower recirculating zonesPerpendicular flow has lower wind speed, higher temperature because of recirculating zones

Parallel Flow VS. Perpendicular Flow 37


Wind direction plays a major role in keeping the canyon air temperature low as demonstrated by the simulation, where the parallel direction gives the best performance (because of no obstruction).

Hence, the porosity (especially at pedestrian height) of the urban form will likely play a major role in determining how much heat can be transported out from the canyon.

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FUTURE WORK

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FUTURE WORK

Other urban morphologies / geometric variables will be explored togetherto find their correlations to urban ventilationand air temperature of pedestrian heigt.

Considering EUI (Energy Use Intensity)rejecting from building rooftops as well(QB).

Key density and morphology variables.

ACKNOWLEDGEMENTThis research programme / project is funded by the National Research Foundation Singapore under its

Campus for Research Excellence and Technology Enterprise (CREATE) programme.

THANK YOU!

Q & A

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Fighting Urban Heat Island (UHI) and Climate Change through Mitigation

and Adaptation

www.ic2uhi2016.org30 – 31 MAY AND 1 JUNE 2016

NATIONAL UNIVERSITY OF S INGAPORE

FOURTH INTERNATIONAL CONFERENCE ON COUNTERMEASURES TO URBAN HEAT ISLAND

4TH IC2UHI 2016

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http://www.ic2uhi2016.org/

INCREASE AT PEDESTRIAN HEIGHT IN … HEAT CONTRIBUTION TO AIR TEMPERATURE INCREASE AT PEDESTRIAN...

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